Light-Interband transitions coupling in Aluminum
Examensarbete för masterexamen
Canales Ramos, Adriana Ivonne
Light-matter interactions may be described as the energy transfer between an electronic transition (emitter or two-level system) and an optical cavity. In weak interactions such transfer is mainly from one component to the other. Thus, the transition rate of the two-level system can be changed, via the so-called Purcell effect. Whereas strong interactions are characterized by a reversible energy transfer between the components and giving rise to a hybrid system with properties different than the original components. This allows to tailor fundamental properties of matter by strongly coupling the transition to light . This work studied the interaction between interband transitions (IBTs) in Aluminum and resonances of two different kind of cavities: plasmonic nanodisks and asymmetric microcavities in a perfect absorber configuration. The system is peculiar because the cavity is coupled to an intrinsic transition of the material that composes it. Calculations using Drude-Lorentz model for the dielectric function of Al were perfomed to model the coupling on both cavities. Extinction and scattering spectra were calculated for nanodisks, and reflectivity spectra for microcavities. Both systems were fabricated and optically characterized by taking extinction, scattering, and reflection spectra of the samples. The resulting interactions between IBTs and the two cavity modes were weak, which is enough to modify the absorption rate of the IBTs, but not enough to change fundamental properties of Al. Calculations suggest that by improving Al quality during deposition, the interaction gets stronger, such that it is on the edge of strong coupling. A surprising result of this work is the potential of asymmetric microcavities as open cavities to study light-matter interactions even without the contribution of IBTs.
Fysik , Physical Sciences